Agricultural seeders are used to place seed and fertilizer in the soil to plant a crop. It is necessary to place the seed at a substantially consistent depth beneath the surface of the soil. Opener arms of various configurations typically extend downward from the seeder frame and a seed furrow opener is mounted on the opener arm and adapted to engage the soil to make a seed furrow into which the seed is deposited. Typically the furrow opener pushes soil to one or both sides and seed is deposited close behind the furrow opener so that the pushed aside soil can then fall back in on top of the seed. A packer wheel is typically provided following the seed furrow opener and oriented to roll over the seed furrow to pack the soil that has fallen back over the seed and encourage seed germination.
The desired seed depth is typically relatively shallow, from less than one inch with some seeds and soil conditions up to three inches or more in others. Since agricultural seeders are commonly 50 or more feet wide and can include 60 or more individual seed furrow openers, consistently maintaining seed depth for each furrow opener in a range of fractions of an inch presents a considerable challenge.
In order to maintain consistent seed depth, it is known to pivotally attach the front end of a trailing arm to the seeder such that same extends generally rearward and downward from the frame and can pivot up and down with respect to the seeder frame. A packer wheel is then rotatably attached to support the rear end of the trailing arm. A seed furrow opener is attached to the trailing arm ahead of the packer wheel such that the vertical position of the bottom of the seed furrow opener with respect to the bottom of the packer wheel can be fixed at a desired location to set the depth of the seed furrow. A bias element is provided to push or pull downward on the trailing arm to engage the seed furrow opener in the soil and force the packer wheel against the ground. The furrow opener assemblies are spaced laterally along the width of the implement by mounting the front ends of the trailing arms to lateral frame members of the implement.
The packer wheel pushes down the soil over the seed in the seed furrow and the bottom of the packer wheel corresponds to the soil surface. The depth of the seed furrow is substantially determined by the vertical distance that the bottom end of the seed furrow opener extends below the bottom of the packer wheel. Such a trailing arm seed furrow opener assembly is disclosed for example in U.S. Pat. No. 5,609,114 to Barton, particularly in FIG. 4B thereof.
Seeders are well known that deposit seed and fertilizer in the soil at the same time. Such seeders can be configured to deposit the seed and fertilizer in the same location or furrow when the amount of fertilizer being deposited is relatively low. With higher fertilizer rates it is required to separate the seed furrow from the fertilizer furrow to avoid damage to the seed that is commonly known to be caused by proximity to larger amounts of fertilizer. The seeder must then also be configured to maintain the seed and fertilizer at consistent locations with respect to each other as well as with respect to the soil surface although the depth of fertilizer placement in the soil is generally considered to not be as critical as seed depth, since the plant roots will reach the fertilizer so long as it is generally close to the seed.
The Barton U.S. Pat. No. 5,609,114 thus also discloses the addition of a fertilizer furrow opener on the trailing arm. A forward disc furrow opener forms a fertilizer furrow, and a rear disc furrow opener nearest to the packer wheel forms a seed furrow above and to one side of the fertilizer furrow to provide separation between the seed and fertilizer.
Similarly, U.S. Pat. No. 5,396,851 to Beaujot discloses a furrow opener assembly like that of Barton with a trailing arm supported by a packer wheel and a hoe-type rear seed furrow opener attached to the trailing arm near the packer wheel and also including a hoe-type front fertilizer furrow opener attached to the trailing arm. The Beaujot apparatus also deposits seed in a seed furrow generally above and to one side of the fertilizer furrow.
A problem occurs with trailing arm furrow opener assemblies such as that of Barton and Beaujot in uneven terrain where the distance between the frame and the ground varies. As the vertical distance of the frame above the ground varies the trailing arm moves up and down about its pivotal attachment to the seeder and the angle of the trailing arm changes and the actual depth of the seed furrow varies. This variation is minimized by locating the seed furrow opener as close as possible to the packer wheel. If in fact the seed furrow opener could be moved back to coincide with the bottom of the packer wheel the problem would not arise at all.
Some seeders, such as that disclosed in U.S. Pat. No. 4,760,806 to Bigbee do provide a depth controlling gauge wheel mounted to a bracket holding the seed furrow opener and directly beside the seed furrow opener such that the depth control wheel directly determines the depth of the seed furrow. A separate packer wheel or like packing means must then be provided since the gauge wheel is beside the seed furrow.
Placing the rear seed furrow opener close to the packer wheel reduces the time available for soil to fall back into the seed furrow on top of the seed before being packed by the packer wheel. Thus operating speeds must be kept fairly low to allow time for the soil to fall back into the seed furrow before the packer wheel arrives. Thus placing the seed furrow opener close to the packer wheel improves the consistency of the seed furrow depth, but reduces operating speed. While variations in seed furrow depth are minimized, the depth of the fertilizer furrow made by the fertilizer furrow opener located well in front of the seed furrow opener varies significantly in rolling terrain. While fertilizer depth is not as critical as seeding depth, excessive depth is not required or desirable, and also greatly increases the force required to pull the fertilizer furrow opener through the soil, wasting fuel. In some uneven terrain the separation distance between the seed and fertilizer furrows will be reduced at some locations, such that fertilizer damage to the seed can occur in those locations.
Parallel link mechanisms are used in seeders to maintain various furrow opener assemblies or portions thereof in a parallel relationship as they move up and down. For example U.S. Pat. Nos. 5,161,472 to Handy and 5,562,054 to Ryan show furrow opener assemblies with front and rear furrow openers. The rear furrow opener is attached by a parallel link mechanism to a downward extending shank to which the front furrow opener is attached. The rear furrow opener is fixed relative to a packer wheel, and forced down toward the ground by a spring bias element. Thus the depth of penetration of the front furrow opener varies as the front furrow opener shank moves with the frame up and down with respect to the ground surface in rolling terrain, however the rear furrow opener and packer wheel move up and down together with the packer wheel maintaining contact with the ground maintaining a consistent depth for the furrow formed by the rear furrow opener.
The parallel link mechanism maintains the bottom of the packer wheel and the bottom of the rear furrow opener substantially at the same relative level, such that there is little variation in the depth of the seed furrow as the vertical position of the parallel link mechanism varies. The gauge wheel does not control the vertical position of the front furrow opener and shank which typically is pivotally attached to the seeder such that same can move with respect to the seeder.
U.S. Pat. No. 6,408,772 to Lempriere discloses a blade mounted on a parallel link mechanism. Conduits are defined inside the blade to separately dispense seed, fertilizer, water, and the like through different locations from front to rear and laterally along the bottom of the blade. Although no packer wheel is shown in the Lempriere patent, in production models it is known to mount a packer wheel on the parallel link mechanism behind the blade to pack and control depth as discussed above. Since the blade is a single unit, the depth adjustment provided by the packer wheel is the same for all products dispensed by the blade.
Parallel link mechanisms are also known for mounting row crop and cultivating units or rigs on an implement frame, for example as disclosed in U.S. Pat. Nos. 6,325,156 to Barry, 5,520,125 to Thompson, and 5,333,559 to Hodapp et al. These units comprise generally a front gauge wheel or wheels and a following ground engaging tool such as a furrow opener or sweep. A bias element forces the parallel link mechanism downward.
U.S. Pat. No. 5,351,635 to Hulicsko discloses a support frame mounted to a seeder frame by a parallel link mechanism and supported by a front wheel and two rear packer wheels. A bias element forces the support frame down toward the ground. A furrow opener shank is pivotally attached to the support frame so as to be able to move up and down independent of rear packer wheels and a further bias element exerts a force on the shank urging it downward.